Alpine Sites Research Articles

Exploring environmental and physiological drivers of the annual carbon budget of biocrusts from various climatic zones with a mechanistic data-driven model

Abstract. Biocrusts are a worldwide phenomenon, contributing substantially to ecosystem functioning. Their growth and survival depend on multiple environmental factors, including climatic ones, and the relations of these factors to physiological processes. Responses of biocrusts to individual environmental factors have been examined in a large number of field and laboratory experiments. These observational data, however, have rarely been assembled into a comprehensive, consistent framework that allows quantitative exploration of the roles of multiple environmental factors and physiological properties for the performance of biocrusts, in particular across climatic regions. Here we used a data-driven mechanistic modelling framework to simulate the carbon balance of biocrusts, a key measure of their growth and survival. We thereby assessed the relative importance of physiological and environmental factors for the carbon balance at six study sites that differ in climatic conditions. Moreover, we examined the role of seasonal acclimation of physiological properties using our framework, since the effects of this process on the carbon balance of biocrusts are poorly constrained so far. We found substantial effects of air temperature, CO2 concentration, and physiological parameters that are related to respiration on biocrust carbon balance, which differ, however, in their patterns across regions. The ambient CO2 concentration is the most important factor for biocrusts from drylands, while air temperature has the strongest impact at alpine and temperate sites. Metabolic respiration cost plays a more important role than optimum temperature for gross photosynthesis at the alpine site; this is not the case, however, in drylands and temperate regions. Moreover, we estimated a small annual carbon gain of 1.5 gm-2yr-1 by lichen-dominated biocrust and 1.9 gm-2yr-1 by moss-dominated biocrust at a dryland site, while the biocrusts lost a large amount of carbon at some of the temperate sites (e.g. −92.1 for lichen-dominated and −74.7 gm-2yr-1 for moss-dominated biocrust). These strongly negative values contradict the observed survival of the organisms at the sites and may be caused by the uncertainty in environmental conditions and physiological parameters, which we assessed in a sensitivity analysis. Another potential explanation for this result may be the lack of acclimation in the modelling approach, since the carbon balance can increase substantially when testing for seasonally varying parameters in the sensitivity analysis. We conclude that the uncertainties in air temperature, CO2 concentration, respiration-related physiological parameters, and the absence of seasonal acclimation in the model for humid temperate and alpine regions may be a relevant source of error and should be taken into account in future approaches that aim at estimating the long-term biocrust carbon balance based on ecophysiological data.

Distinct taxonomic and functional profiles of high Arctic and alpine permafrost-affected soil microbiomes

BackgroundGlobal warming is affecting all cold environments, including the European Alps and Arctic regions. Here, permafrost may be considered a unique ecosystem harboring a distinct microbiome. The frequent freeze–thaw cycles occurring in permafrost-affected soils, and mainly in the seasonally active top layers, modify microbial communities and consequently ecosystem processes. Although taxonomic responses of the microbiomes in permafrost-affected soils have been widely documented, studies about how the microbial genetic potential, especially pathways involved in C and N cycling, changes between active-layer soils and permafrost soils are rare. Here, we used shotgun metagenomics to analyze the microbial and functional diversity and the metabolic potential of permafrost-affected soil collected from an alpine site (Val Lavirun, Engadin area, Switzerland) and a High Arctic site (Station Nord, Villum Research Station, Greenland). The main goal was to discover the key genes abundant in the active-layer and permafrost soils, with the purpose to highlight the potential role of the functional genes found.ResultsWe observed differences between the alpine and High Arctic sites in alpha- and beta-diversity, and in EggNOG, CAZy, and NCyc datasets. In the High Arctic site, the metagenome in permafrost soil had an overrepresentation (relative to that in active-layer soil) of genes involved in lipid transport by fatty acid desaturate and ABC transporters, i.e. genes that are useful in preventing microorganisms from freezing by increasing membrane fluidity, and genes involved in cell defense mechanisms. The majority of CAZy and NCyc genes were overrepresented in permafrost soils relative to active-layer soils in both localities, with genes involved in the degradation of carbon substrates and in the degradation of N compounds indicating high microbial activity in permafrost in response to climate warming.ConclusionsOur study on the functional characteristics of permafrost microbiomes underlines the remarkably high functional gene diversity of the High Arctic and temperate mountain permafrost, including a broad range of C- and N-cycling genes, and multiple survival and energetic metabolisms. Their metabolic versatility in using organic materials from ancient soils undergoing microbial degradation determine organic matter decomposition and greenhouse gas emissions upon permafrost thawing. Attention to their functional genes is therefore essential to predict potential soil-climate feedbacks to the future warmer climate.

Characterization of rock glaciers environments combining structurally-coupled and petrophysically-coupled joint inversions of electrical resistivity and seismic refraction datasets

The degradation of mountain permafrost is well documented at many Alpine sites. Geophysical techniques have been intensively used to monitor these sites, since permafrost degradation is not only a proxy of climate change and global warming but also a possible source of slope instabilities and triggering of mass movements. While the use of non-invasive geophysical techniques is promising, the interpretation of different geophysical results can introduce ambiguities in defining the investigated subsoil and often does not lead to a quantitative estimation of the internal permafrost constituents (rock matrix, ice, liquid water and air contents). To overcome these limitations, we applied an optimized joint inversion approaches of electrical resistivity and refraction seismic tomography datasets collected at two Swiss rock glaciers (Schafberg - Canton Grisons, and Ritigraben - Canton Valais). Firstly, to improve the structural interpretation of the frozen near subsurface, we performed a structurally coupled cooperative joint inversion, optimizing the coupling parameters. Subsequently, we used the petrophysical joint inversion to quantify the composition of these mountain permafrost substrates, optimizing the numerical and petrophysical parameters. The obtained results agree with field observations and the borehole data collected at these two sites, opening new perspectives for the future quantitative monitoring of permafrost constituents. Plain language summaryIncreasing mean annual temperatures over the last decades has led to glacier melt and permafrost thawing. The degradation of glaciers is easier to quantify as they are visible on the surface, as opposed to permafrost which is found in the subsoil and must therefore be studied with direct drilling techniques or with non-invasive geophysical methods. Drilling investigations are expensive and complicated to perform in high mountain environments and only provide 1D information. Geophysical surveys can be used to quickly and economically characterize larger areas. Since permafrost thawing is a risk factor in high mountain environments (inducing e.g. instability of infrastructure, or triggering rock falls and landslides), it is important to have reliable geophysical techniques to study these environments. In this work, we propose an optimization of two different data analysis processes, applied to geoelectrical and seismic measurements, to better define the structure and composition of two ice-rich mountain permafrost sites in the Swiss Alps.

Chemical Characteristics and Source Apportionment of Biogenic Primary and Secondary Organic Aerosols in an Alpine Ecosystem of Tibetan Plateau

AbstractThe knowledge about the chemical characteristics of organic aerosols in alpines were still limited. Fifty samples were collected in an alpine site in Tibetan Plateau during May 2015 and April 2016 to measure the concentrations of sugar and biogenic secondary organic aerosol (BSOA) compounds. The annual mean concentrations of anhydrosugar, primary sugars, and sugar alcohols in Mt. Gongga were 86.6 ± 43.1, 168 ± 40.0 and 204 ± 62.9 ng/m3, respectively. All of the anhydrosugars displayed the highest concentrations in winter, followed by spring, autumn, and the lowest ones in summer, which was contributed by dense biomass burning (BB) in winter. In contrast, nearly all of the primary sugar and sugar alcohol levels peaked in summer, which might be associated with the higher rates of vegetation growth and microbial metabolic activities during the warming season. The levels of BSOA tracers also suffered from markedly seasonal variations. The sesquiterpene SOA displayed the highest level in winter (27.3 ± 16.8 ng/m3), which might be associated with the biomass burning in the surrounding regions. However, most of the species of isoprene and monoterpene SOA tracers suffered from the higher levels in summer, which was contributed by the higher biogenic volatile organic compounds (BVOC) emission and reaction rates. Based on source apportionment result, BB (26%) was the dominant contributor to sugar and BSOA species in Mt. Gongga, followed by airborne pollen (24%), plant release (19%), soil emission (13%), fungal spore (9%), and isoprene oxidation (8%). The result of this study reveals mixed contributions of BB and vegetation emission promote the formation of biogenic organic aerosols in Tibetan Plateau.

Particle Number Size Distribution of Wintertime Alpine Aerosols and Their Activation as Cloud Condensation Nuclei in the Guanzhong Plain, Northwest China

AbstractThe particle number size distribution (PNSD) and hygroscopicity on alpine sites can directly reflect the interaction between aerosol and cloud in the free troposphere, and narrow the errors caused by extrapolation from the ground observation. In this study, PNSD and cloud condensation nuclei (CCN) concentration (NCCN) were observed at the summit of Mt. Hua from December 16, 2020, to January 23, 2021. The result showed that the modes and hygroscopicity parameters (κ) of aerosols were significantly affected by the height and direction of the originated air masses. The particle in nucleation mode from new particle formation erupted frequently in 13:00–18:00 local time due to the intense photochemistry and had a potential contribution to CCN through the process of the growth with the ratio of 0.83 nm·h−1, which was affected by air masses, meteorological conditions, and gaseous pollutants. Subsequently, the hygroscopicity κ varied from 0.22 to 0.13 with the supersaturation from 0.2% to 1.0% as more components that were difficult to dissolve or had low hygroscopicity. The comprehensive analysis of PNSD and hygroscopicity showed that smaller k from two‐parameter power model corresponded to particles with higher hygroscopicity or larger diameter, while larger k matched to the hydrophobic or ultrafine particles. In addition, the interactions between aerosol and cloud were estimated more accurately and the uncertainty of indirect effect was shrunk. Overall, we provided insights into PNSD and hygroscopicity of alpine aerosol particles by direct observation on Mt. Hua, which may be important to other elevated regions as well.

Influence of vegetation on occurrence and color of snow algal blooms in Mt. Gassan, Yamagata Prefecture, Japan

ABSTRACT Snow algae are photosynthetic microbes growing on melting snow surfaces, the blooms of which are visible on alpine snowpacks in Japan during the melting season. We characterized the seasonal and altitudinal variations in algal blooms on Mount Gassan, Japan, to assess the influence of vegetation on the algal bloom. From May to July in 2019, we collected colored snow from lower deciduous forest to the upper alpine areas. In the lower forest area, chlorophyll-a concentration in colored snow samples increased concomitantly with deciduous tree budburst, whereas in the alpine area, chlorophyll-a increased from June to July, although at lower levels than in the forest area. The absorption spectra of algal pigments extracted from samples differed among study sites and seasons, with those obtained from forest sites mainly characterized by absorption of chlorophylls and primary carotenoids, whereas those from alpine sites showed an intense secondary carotenoid peak throughout the study period. Chemical solute analyses revealed a general abundance of phosphate in snow, which was significantly higher in forest than in alpine sites and positively correlated with chlorophyll-a concentration. These findings suggest that nutrient supply from the forest canopy largely controls the appearance of colored snow in this area.

Seasonal forecasting of snow resources at Alpine sites

Abstract. Climate warming in mountain regions is resulting in glacier shrinking, seasonal snow cover reduction, and changes in the amount and seasonality of meltwater runoff, with consequences on water availability. Droughts are expected to become more severe in the future with economical and environmental losses both locally and downstream. Effective adaptation strategies involve multiple timescales, and seasonal forecasts can help in the optimization of the available snow and water resources with a lead time of several months. We developed a prototype to generate seasonal forecasts of snow depth and snow water equivalent with a starting date of 1 November and a lead time of 7 months, so up to 31 May of the following year. The prototype has been co-designed with end users in the field of water management, hydropower production and mountain ski tourism, meeting their needs in terms of indicators, time resolution of the forecasts and visualization of the forecast outputs. In this paper we present the modelling chain, based on the seasonal forecasts of the ECMWF and Météo-France seasonal prediction systems, made available through the Copernicus Climate Change Service (C3S) Climate Data Store. Seasonal forecasts of precipitation, near-surface air temperature, radiative fluxes, wind and relative humidity are bias-corrected and downscaled to three sites in the Western Italian Alps and finally used as input for the physically based multi-layer snow model SNOWPACK. Precipitation is bias-corrected with a quantile mapping method using ERA5 reanalysis as a reference and then downscaled with the RainFARM stochastic procedure in order to allow an estimate of uncertainties due to the downscaling method. The impacts of precipitation bias adjustment and downscaling on the forecast skill have been investigated. The skill of the prototype in predicting the deviation of monthly snow depth with respect to the normal conditions from November to May in each season of the hindcast period 1995–2015 is demonstrated using both deterministic and probabilistic metrics. Forecast skills are determined with respect to a simple forecasting method based on the climatology, and station measurements are used as reference data. The prototype shows good skills at predicting the tercile category, i.e. snow depth below and above normal, in the winter (lead times: 2–3–4 months) and spring (lead times: 5–6–7 months) ahead: snow depth is predicted with higher accuracy (Brier skill score) and higher discrimination (area under the relative operating characteristics (ROC) curve skill score) with respect to a simple forecasting method based on the climatology. Ensemble mean monthly snow depth forecasts are significantly correlated with observations not only at short lead times of 1 and 2 months (November and December) but also at lead times of 5 and 6 months (March and April) when employing the ECMWFS5 forcing. Moreover the prototype shows skill at predicting extremely dry seasons, i.e. seasons with snow depth below the 10th percentile, while skills at predicting snow depth above the 90th percentile are model-, station- and score-dependent. The bias correction of precipitation forecasts is essential in the case of large biases in the global seasonal forecast system (MFS6) to reconstruct a realistic snow depth climatology; however, no remarkable differences are found among the skill scores when the precipitation input is bias-corrected, downscaled, or bias-corrected and downscaled, compared to the case in which raw data are employed, suggesting that skill scores are weakly sensitive to the treatment of the precipitation input.

Blue-stain development on Norway spruce logs under alpine conditions

Discoloration of the sapwood caused by blue-stain fungi on conifer logs during interim storage causes significant loss to the forest industry. The fungal infection is often associated with bark beetle attacks because the spores are transmitted by the beetles. They can also be disseminated by rain-splash and moist air. While there are methods to protect logs from sap-stain in wood yards, this is often not possible in the forest for practical and regulatory reasons. Timing of harvesting and timely transportation are often the only ways to prevent blue-stain. To estimate the urgency of transportation, knowledge of the growth of blue-stain fungi and its dependence on weather conditions is of great interest. The proportion of discolored sapwood on Norway spruce logs was recorded along a time series, together with weather data in two field experiments conducted in spring and summer at two alpine sites in Austria. A predictive model was developed to estimate the proportion of blue-stained sapwood based on the temperature sum to which the logs were exposed. After harvest in March, there was a time lag of 82 and 97 days at the two respective sites, caused by initially low temperatures, before discoloration started. In contrast, sap-stain occurred 14 days after the harvest in June, when warm conditions prevailed from the start. The nonlinear least square regression model can help to estimate a window of opportunity to transport wood before it loses its value and serves as a sub model for lead time estimation within logistic decision support systems.

Soil organic matter changes under experimental pedoclimatic modifications in mountain grasslands of the French Alps

Mountain grasslands contain large stocks of soil organic carbon (SOC), of which a good part is in labile particulate form. This labile SOC may be protected by cold climate that limits microbial activity. Strong climate change in mountain regions threatens to destabilize these SOC stocks. However, so far the climate response of SOC stocks in mountain grasslands remains highly uncertain, under either warming or cooling conditions. To overcome this knowledge gap, we studied the effect of pedoclimatic regime changes on topsoil (0–10 cm) SOC in two complementary experiments: 3 °C of warming or cooling by reciprocal transplanting to an alpine (2450 m a.s.l.) and a subalpine (1950 m a.s.l.) grassland and 1 °C of warming by open-top chambers in the same grasslands.Topsoil SOC stocks were higher at the alpine site than at the subalpine site, and the biogeochemical signature of the soil organic matter (SOM) also differed between the two study sites. SOM was O-enriched, H-depleted, and more thermally stable at the warmer subalpine site. After three years, abrupt warming by transplanting tended to decrease topsoil SOC content. The remaining SOC was characterized by a more thermostable signature. This result suggests the preferential depletion of labile SOC upon experimental topsoil warming. Cooling did not modify overall SOC content but uphill transplanted topsoils showed a more thermolabile biogeochemical signature. In contrast, open-top chamber warming of alpine and subalpine topsoils caused limited changes to SOC stocks and SOM biogeochemical signature, possibly because the induced pedoclimatic change was more limited and more gradual compared to the warming by transplantating which reduced the annual snow cover period by around 60 days and increased cumulative degree days by a factor of ten as compared to the OTC-induced warming. Gradual temperature changes may take longer to become effective than a shock transplant treatment. We conclude that SOC in mountain grassland topsoils can be highly reactive to climate shocks.

Use of remote sensing and bio-geochemical models to estimate the net carbon fluxes of managed mountain grasslands

The current paper presents a methodology which can simulate the net carbon fluxes of semi-natural grasslands based on the combination of a parametric and a bio-geochemical model. The first model (modified C-Fix) estimates grassland gross primary production (GPP) by driving the light use efficiency approach with remotely sensed normalized difference vegetation index (NDVI) data. The latter model (BIOME-BGC) simulates all main ecosystem processes based on meteorological and ancillary data. The outputs of the two models are finally combined and corrected for the effects of human-induced biomass changes (i.e. mowing, grazing, etc.). The modelling strategy, fed with ancillary and MODIS NDVI data, is tested in two semi-natural grasslands, the first (Amplero) on the Apennines and the second (Monte Bondone) on the Alps (Central and Northern Italy, respectively). The two sites, which show diversified eco-climatic conditions and are managed differently (i.e. Amplero by spring mowing plus cattle grazing and Monte Bondone by summer mowing), were selected for the availability of eddy covariance observations of GPP and net ecosystem production (NEP) collected during several years (from 2003 to 2012). These observations were used to assess the estimates of the modelling strategy, obtaining promising results for both study sites. The greatest estimation errors are found in the Alpine site and are mostly induced by the inaccurate detection of local grassland NDVI values, which is due to the insufficient spatial and temporal resolutions of the used MODIS NDVI imagery. The results of the study highlight the importance of information on the local management practices applied, which is decisive for quantifying medium-term changes in net carbon fluxes.

The International Tundra Experiment (ITEX): 30 years of research on tundra ecosystems

The International Tundra Experiment (ITEX) was founded in 1990 as a network of scientists studying responses of tundra ecosystems to ambient and experimental climate change at Arctic and alpine sites across the globe. Common measurement and experimental design protocols have facilitated synthesis of results across sites to gain biome-wide insights of climate change impacts on tundra. This special issue presents results from more than 30 years of ITEX research. The importance of snow regimes, bryophytes, and herbivory are highlighted, with new protocols and studies proposed. The increasing frequency and magnitude of extreme climate events is shown to have strong effects on plant reproduction. The most consistent plant trait response across sites is an increase in vegetation height, especially for shrubs. This will affect surface energy balance, carbon and nutrient dynamics and trophic level interactions. Common garden studies show adaptation responses in tundra species to climate change but they are species and regionally specific. Recommendations are made including establishing sites near northern communities to increase reciprocal engagement with local knowledge holders and establishing multi-factor experiments. The success of ITEX is based on collegial cooperation among researchers and the network remains focused on documenting and understanding impacts of environmental change on tundra ecosystems.

Seedling performance, phenotypic traits and growing media for domestication of Lilium polyphyllum

Societal Impact StatementMedicinal plants are a key component of primary health care for much of the world's population. However, overharvesting and indiscriminate collection from the wild threatens medicinal plant populations with extinction. One conservation solution to preserve biodiversity is to domesticate and cultivate threatened medicinal plants, in order to provide a sustainable source close to the local populations who use the species. Here, we present work to cultivate the critically endangered (CR) medicinal herb, Lilium polyphyllum. To reduce unsustainable wild harvesting, we identify different climatic zones, habitats and growing media, which will aid domestication of this endangered species and help local populations to cultivate the plant near its natural habitat.Summary Lilium polyphyllum (Liliaceae) is a perennial, bulbous medicinal herb, used in more than 30 Ayurvedic medicinal formulations as an aphrodisiac, galactagogue and anti‐ageing agent. The species is categorized as critically endangered on the IUCN (International Union for Conservation of Nature) Red List due to habitat degradation and unregulated collection. To alleviate the pressure on wild populations and increase conservation, the IUCN Red List recommends its domestication in suitable habitats. The present study was carried out over three consecutive years to evaluate the performance and survival of the species in two agro‐climatic zones in Garhwal Himalaya, Uttarakhand, India. L. polyphyllum seedlings were raised and transplanted into different growing mediums and treatments (control, manure, litter and polyhouse) in both temperate (Pothivasa, 2200 m a.s.l.) and alpine (Tungnath, 3600 m a.s.l.) regions to identify a suitable site and or habitat for future mass production. Experiments revealed yield and performance in polyhouse beds were greatest in the temperate region. Plant survival was also high in polyhouse beds in both the temperate (81%) and alpine (40%) sites. Phenotypic and growth traits of plants grown from bulbs collected from the wild population of the temperate site performed better in both morphology and in yield than those in the alpine site after one growing season. Cocopeat and sand may be responsible for the improved growth of plants. In conclusion, plant survival rate, growth performance and yield under polyhouse conditions were higher in lower altitudes (temperate regions), which may provide a production centre for seedlings to interested farmers in other regions.

Thermodynamic basis for the demarcation of Arctic and alpine treelines

At the edge of alpine and Arctic ecosystems all over the world, a transition zone exists beyond which it is either infeasible or unfavorable for trees to exist, colloquially identified as the treeline. We explore the possibility of a thermodynamic basis behind this demarcation in vegetation by considering ecosystems as open systems driven by thermodynamic advantage—defined by vegetation’s ability to dissipate heat from the earth’s surface to the air above the canopy. To deduce whether forests would be more thermodynamically advantageous than existing ecosystems beyond treelines, we construct and examine counterfactual scenarios in which trees exist beyond a treeline instead of the existing alpine meadow or Arctic tundra. Meteorological data from the Italian Alps, United States Rocky Mountains, and Western Canadian Taiga-Tundra are used as forcing for model computation of ecosystem work and temperature gradients at sites on both sides of each treeline with and without trees. Model results indicate that the alpine sites do not support trees beyond the treeline, as their presence would result in excessive CO_2 loss and extended periods of snowpack due to temperature inversions (i.e., positive temperature gradient from the earth surface to the atmosphere). Further, both Arctic and alpine sites exhibit negative work resulting in positive feedback between vegetation heat dissipation and temperature gradient, thereby extending the duration of temperature inversions. These conditions demonstrate thermodynamic infeasibility associated with the counterfactual scenario of trees existing beyond a treeline. Thus, we conclude that, in addition to resource constraints, a treeline is an outcome of an ecosystem’s ability to self-organize towards the most advantageous vegetation structure facilitated by thermodynamic feasibility.

Accuracy of UAV Photogrammetry in Glacial and Periglacial Alpine Terrain: A Comparison With Airborne and Terrestrial Datasets

Unoccupied Aerial Vehicles (UAVs) equipped with optical instruments are increasingly deployed in high mountain environments to investigate and monitor glacial and periglacial processes. The comparison and fusion of UAV data with airborne and terrestrial data offers the opportunity to analyse spatio-temporal changes in the mountains and to upscale findings from local UAV surveys to larger areas. However, due to the lack of gridded high-resolution data in alpine terrain, the specific challenges and uncertainties associated with the comparison and fusion of multi-temporal data from different platforms in this environment are not well known. Here we make use of UAV, airborne, and terrestrial data from four (peri)glacial alpine study sites with different topographic settings. The aim is to assess the accuracy of UAV photogrammetric products in complex terrain, to point out differences to other products, and to discuss best practices regarding the fusion of multi-temporal data. The surface geometry and characteristic geomorphological features of the four alpine sites are well captured by the UAV data, but the positional accuracies vary greatly. They range from 15 cm (root-mean-square error) for the smallest survey area (0.2 km2) with a high ground control point (GCP) density (40 GCPs km−2) to 135 cm for the largest survey area (>2.5 km2) with a lower GCP density (<10 GCPs km−2). Besides a small number and uneven distribution of GCPs, a low contrast, and insufficient lateral image overlap (<50–70%) seem to be the main causes for the distortions and artefacts found in the UAV data. Deficiencies both in the UAV and airborne data are the reason for horizontal deviations observed between the datasets. In steep terrain, horizontal deviations of a few decimetres may result in surface elevation change errors of several metres. An accurate co-registration and evaluation of multi-temporal UAV, airborne, and terrestrial data using tie points in stable terrain is therefore of utmost importance when it comes to the investigation of surface displacements and elevation changes in the mountains. To enhance the accuracy and quality of UAV photogrammetry, the use of UAVs equipped with multi-spectral cameras and high-precision positioning systems is recommended, especially in rugged terrain and snow-covered areas.

AIRBORNE LASER SCANNING CHANGE DETECTION FOR QUANTIFYING GEOMORPHOLOGICAL PROCESSES IN HIGH MOUNTAIN REGIONS

Abstract. Disturbance by geomorphic processes is a key factor for current and potential plant species distributions in high mountain regions. We implemented and tested an approach for the detection, quantification, and geomorphological classification of 3D topographic change using airborne laser scanning (ALS) data. This approach is applied to two point cloud epochs (from 2006 and 2017) to identify and analyse changes related to five different process categories in a study area in the European Alps: Fluvial Processes, Rock Glacier Movement & Landslides, Channel Erosion & Debris Flow, Rockfall Release & Deposition and Vegetation & Anthropogenic Change. The results are assessed through comparison with a manually produced geomorphological map. The analysis covering the eleven-year time period provides detailed information on the magnitudes and spatial distribution of change per identified geomorphological process. The study shows that the workflow is capable of providing the fundamental basis for mapping vegetation disturbance by geomorphic activity in a high alpine site.

Variations in fungal community structure along elevation gradients in contrasting Austrian Alpine ecosystems

Soil fungi, as a major decomposer of organic matter, govern carbon (C) cycle and act as crucial regulators of the soil C and nutrient balance in terrestrial ecosystems. Climate change and parent material alter important environmental conditions that may affect fungal community. However, very little is known about the diversity and community structure of soil fungi along elevation gradients with distinct parent material properties. We investigated the effects of climate and vegetation changes on soil fungal diversity and community structure at two Austrian alpine sites with different bedrock properties (limestone at the Hochschwab site and silicate at the Rauris site), but with similar climatic conditions. At these sites we sampled soils from 0 to 25 cm depth along three elevation gradients ranging from 900 to 2100 m above sea level and examined how the fungal communities vary by using Illumina MiSeq sequencing. Our results show that the fungal community structures at the Hochschwab and the Rauris site were defined by elevation-induced changes in vegetation and associated differences in soil pH. In forest soils, symbiotrophic fungi (mainly belonging to the class Agaricomycetes, phylum Basidiomycota) were dominant at the Hoschwab site, while at the Rauris site the Ascomycota were the most dominant phyla. The change to grass dominated vegetation generally increased the contribution of saprotrophic fungi (mainly belonging to various classes of the phylum Mucoromycota) at both elevational sites. Prevalence of ectomycorrhizal fungi and associated lignolytic enzymes induced soil C loss might explain lower soil organic C stocks at the Rauris site compared to the Hochschwab site. Our results suggest that parent material can modulate fungal communities indirectly via vegetation (e.g., litter quality) adapted to particular soil conditions. Therefore, changes in fungal structural composition might exert important consequences on ecosystem C balances.

Climate influence on plant-pollinator interactions in the keystone species Vaccinium myrtillus.

Climate change is altering the world's ecosystems through direct effects of climate warming and precipitation changes but also indirectly through changes in biotic interactions. For instance, climate‐driven changes in plant and/or insect communities may alter plant–pollinator interactions, thereby influencing plant reproductive success and ultimately population dynamics of insect‐pollinated plants. To better understand how the importance of insect pollination for plant fruit set varies with climate, we experimentally excluded pollinators from the partly selfing keystone species Vaccinium myrtillus along elevational gradients in the forest‐tundra ecotone in central Norway. The study comprised three mountain areas, seven elevational gradients spanning from the climatically relatively benign birch forest to the colder alpine areas above the tree line, and 180 plots of 1 × 1 m, with experimental treatments allocated randomly to plots within sites. Within the experimental plots, we counted the number of flowers of V. myrtillus and counted and weighed all fruits, as well as seeds for a selection of fruits. Excluding pollinators resulted in lower fruit production, as well as reduced fruit and seed mass of V. myrtillus. In the alpine sites pollinator exclusion resulted in 84% fewer fruits, 50% lower fruit weight, and 50% lower seed weight compared to control conditions. Contrary to our expectations, the negative effect of pollinator exclusion was less pronounced in the forest compared to alpine sites, suggesting that the importance of insect pollination for seed production is lower at low elevations. Our findings indicate that the keystone species V. myrtillus is relatively robust to changes in the pollinator community in a warmer climate, thereby making it less vulnerable to climate‐driven changes in plant–pollinator interactions.

Reconstruction of the late Holocene climate variability from the summer monsoon dominated Bhagirathi valley, western Himalaya

• High resolution proxy data traced late Holocene climate events for western Himalaya. • Sites have traced dry (4.2 ka; Little Ice Age) phases and moist Medieval warm period . • Dry (weak summer monsoon) phases correspond well with decreased solar irradiance. • Traced dry events are more prominent in drier alpine site than moist temperate site. • LIA phase recorded asynchronous response time in Alpine and Temperate pollen data. This study presents a centennial to decadal scale late Holocene climate scenario from the Indian summer monsoon (ISM) dominated region of western Himalaya. The subsurface sediments analyzed for palynology, carbon isotope (δ 13 C org ) and magnetic susceptibility (χlf) were collected from the temperate and alpine meadows, respectively receiving high (low) and relatively low (high) amount of ISM (winter) precipitation. We could identify the dry and moist phases linked to respective weakening and strengthening of ISM. High frequency of steppe pollen ( Ephedra , Amaranthaceae, Asteraceae, Brassicaceae) between 4.4 and 3.8 ka represented a dry phase, coeval to 4.2 ka global dry event. Subsequent low δ 13 C values and high pollen frequency of moist vegetation (Geraniaceae, Cyperaceae, Apiaceae, Ranunculaceae and pteridophytes) till ca. 0.9 ka suggested moist phase but with an intermittent dry episode ca. 2.9–2.5 ka, allowing rise of steppe taxa. Climate ameliorated ca. 1.8 ka and moist conditions further enhanced between 1.5 and 0.9 ka, corresponding to Medieval Warm Period. Sharp increase in δ 13 C org values and steppe vegetation ca. 0.8 ka attributed to dryness that intensified between 0.6 and 0.2 ka and coincide with Little Ice Age (LIA) anomaly. The recorded dry (weak ISM) phases showed correspondence with the low solar irradiance and supported the teleconnection with north Atlantic circulations. Palynological data from both the valleys complement each other throughout late Holocene time. However, the valleys showed temporal inconsistency in their aridity peaks during LIA phase. This indicates response variability of the two physiographically different sites to summer and winter monsoon systems.

Intraspecific Relationships and Nest Mound Shape Are Affected by Habitat Features in Introduced Populations of the Red Wood Ant Formica paralugubris.

Simple SummaryRed wood ants (Formica rufa goup) are dominant ant species widespread in the Eurasian continent. These species have a strong ecological impact on the habitats they dwell in, being top-ranked predators. One of the most striking features of these ants is represented by the large nest mounds they build. In this study, we investigated how nest mound shape and colony organization of imported populations of Formica paralugubris varied in three different habitat types. We found that nest mounds differed in size, number and shape in the three habitats. In all the three sites, nests were connected by trails of workers, but the size of these nest-networks differed. We also investigated the pattern of intraspecific aggression among ants from different nests, and we showed that aggressiveness was higher within each population than between separate populations, a finding in line with a ‘nasty neighbor’ behavior.Ants belonging to the Formica rufa group build large nest mounds, which aid their survival during severe winters. We investigated whether different environmental features of the habitats affected the nest mound shape and the population structure. We assessed the shape of all the nest mounds and mapped inter-nest trails connecting mounds for three imported populations of Formica paralugubris in three forest habitats: fir-dominated, beech-dominated, and a mixture of fir and beech. Single-nest mounds were averagely smaller and flatter in the beech-dominated forest, probably because of lighter building materials. Nonetheless, by summing the volumes of all interconnected nests, the size was similar among all three sites. In fir- and beech-dominated forests, large nests were also central in the networks, suggesting a central place foraging model with these nests as reference. We finally performed aggression tests, and found that aggressiveness was significantly higher among nests belonging to the same population than between populations. The results highlight the plasticity of the species to adapt nest and colony structure to different environments. Additionally, it appears that none of these populations is unicolonial, as observed in various alpine sites, there and the observed patterns of aggression are coherent with the ‘nasty neighbor’ effect.

Nutrient Analysis and Species Diversity of Alpine Grasslands: A Comparative Analysis of Less Studied Biodiversity Hotspots

The alpine grasslands of Kashmir Himalaya act as a treasure house of floristic biodiversity. They have remained largely unstudied because of their remoteness and inaccessibility. It is imperative to have quantitative studies of these areas to allow the long-term monitoring of flora in these fragile ecosystems. During the present study, nutrient analysis and species diversity of some alpine grasslands were investigated. Electroconductivity (EC) of the soils ranged between 0.12 and 0.33 (dSm−1). With an increase in altitude and precipitation and a decrease in temperature, soil pH and available macro-nutrients (OC, N, P, K) show a considerable decrease. Sixty-six plant species belonging to twenty-nine families and fifty-one genera were reported with members predominantly from the Asteraceae, Rosaceae and Plantaginaceae families. Seven species were common to all study areas and Renyi diversity profiles showed that Kongwattan was the most diverse followed by Poshpathri and Yousmarg. The results of the Sorensen β diversity index showed a relatively lower dissimilarity index among the three studied alpine sites. In the majority of the growth forms, growth initiation was recorded in April, whereas senescence occurred in September. The highest bloom was seen in June-July. The plant species exhibited a greater variability in their phenophases under different environmental conditions and altitudinal gradients. Plants were more vigorous at lower altitudes and showed rapid response to the prevailing conditions. Stoloniferous forbs and tussock forming graminoids such as Sibbaldia cuneata, Trifolium repens, Plantago major, Trifolium pratense, Poa compressa, Poa angustifolia, and Plantago lanceolata showed a greater importance value index (IVI). The sedentary system of livestock rearing at Yousmarg resulted in the decreased density of the palatable species. This study allowed us to conclude that direct knowledge of soil nutrient composition and species diversity in alpine ecosystems can enhance conservation and ensure better management practices over a period of time.